Switching power supply controller with high frequency current balance

Abstract

A controller for a multi-phase switching power supply shuffles the sequence of the phases in response to a load transient to prevent synchronization of one or more phases with high-frequency load transients. The sequence may be shuffled by varying the frequency and/or sequence of the switching control signals to introduce a random variation in the phases.

1. A switching power supply controller comprising:
 a modulation circuit to generate switching control signals to control the output of a multi-phase switching power supply in response to an error signal, the modulation circuit including an oscillator to control the frequency of the switching control signals, the oscillator having an input to set the switching frequency; 
 an error amplifier arranged to generate the error signal in response to the output of the switching power supply and a reference signal; and 
 a diode and a resistor arranged in series between an output of the error amplifier and the input of the oscillator to shuffle the sequence of the switching control signals by increasing the frequency to an increased frequency in response to a load transient and maintaining the increased frequency during the load transient. 
 
     
     
       2. The controller of  claim 1  where the modulator includes a current balance circuit to provide low-frequency current balance by comparing the current of individual phases with an average current of all phases. 
     
     
       3. A switching power supply control system comprising:
 an integrated circuit including a multi-phase PWM switching power supply controller configured to generate switching control signals to control an output of the multi-phase switching power supply system, the multi-phase PWM switching power supply controller having a first terminal to control an oscillator on the integrated circuit, and a second terminal to provide a measure of the output controlled by the integrated circuit; and 
 a diode and a resistor coupled between the first and second terminals to shuffle a sequence of the switching control signals by increasing a frequency of the oscillator to an increased frequency in response to a load transient and maintaining the increased. frequency during the load transient. 
 
     
     
       4. The system of  claim 3  further comprising a second diode connected in series with the diode and the resistor. 
     
     
       5. The system of  claim 3  where the diode and the resistor are external to the integrated circuit.